This invention relates generally to the field of toner cartridges used in electro-photographic copying devices, and more particularly to an improved removable toner seal used to cover the elongated slot in the cartridge through which toner material flows during operation of the copier.
Various seal materials have been used to prevent toner from leaking out of the toner containment assembly, especially during shipping, prior to use of the toner cartridge. These materials have several requirements, including the ability to tear in a straight line, without tapering or reducing the width of the opening, and to be strong enough to prevent bursting of the seal material caused by the weight of the toner and a sudden impact, as could occur in shipping. The resulting unwanted bursting allows toner to leak from the cartridge.
Two common classes of seal materials are polyester and similar films, and ribbon materials, such as extruded polypropylene or extruded polyethylene. Ribbon materials are widely used in toner cartridges that are remanufactured. Such ribbon materials have suitable lengthwise or axial tensile strength, but the nature of the ribbon material is such that it is significantly weaker in a direction lateral to its principal axis, which is the tear direction. This weakness results in relatively low burst strength, but excellent pull-tear direction. The ribbon material is composed of fibers lightly fused together to form a continuous sheet of material. The fibers are fused in parallel alignment. This parallel arrangement creates a fault direction that allows tearing in a straight line.
In the prior art, to overcome the ribbon material weakness ninety degrees from the direction of the fiber alignment, it is known to apply a thin polyester lamination, to the ribbon material to increase its strength in the weak direction to prevent bursting, but this procedure also strengthens the seal in the tear direction. In so doing, the initial tear of the ribbon laminating strip is made more difficult, and if the laminating layer is too strong it overcomes the straight line tearing characteristic of the parallel ribbon fibers, which defeats the purpose of using the ribbon material. One solution for this problem is disclosed in U.S. Pat. No. 5,523,828, in which two small starting cuts are made parallel to the pull strip axis to provide easier tear starting, this being of particular importance with laminated material.